This invention concerns a process and apparatus for applying a smooth coating of a plasticized-sulfur based composition. In particular, the process comprises applying a smooth coat of the plasticized-sulfur composition by spraying the composition through a nozzle using a substantially inert pressurized gas to assist the spraying process.
Plasticized-sulfur based coating compositions are well known. For instance, U.S. Pat. Nos. 4,026,719 and 3,823,019 describe coating compositions comprising plasticized-sulfur. The usual method of applying these coating compositions has been to employ a pressurized spraying system. According to U.S. Pat. No. 3,823,019, "An airless spraying system in which the spraying pessure is maintained below about 35 p.s.i. has been found to be very satisfactory. In addition, the use of spray nozzles that create a spray pattern, but do not overly atomize the coating composition are preferred. The use of atomizing air, as employed in conventional paint spray operations is undesirable because of the undue generation of vapors and mist."
However, conventional spray nozzles do not provide a particularly smooth coating. The plasticized-sulfur coating compositions tend to form droplets which, although flattening somewhat upon impact, result in a relatively non-uniform coating. Thus, where aesthetic or other considerations demand a smooth uniform coating, conventional means and apparatus are unsatisfactory. Of course, an experienced technician by regulating the flow rate of the composition and by regulating the rate of application can exercise some control over the appearance of the surface. Nevertheless, a more consistent process for applying smooth coating would be an important advance in the field.